Rust deposits on rims from Carbon Ceramic brakes after a track day

[JoeLuck]

Ok I know that CC brakes don't rust, but that is just the rotor. I assume the pads have some metal and would rust. After a track day wash, I have a lot of brown dust (which look like rust) on my wheels. I cleaned the rims yesterday and after one highway drive the wheels are coated in the brown dust again. I am worried that it may be rust, but no clue from where.

I am thinking this rust could be from the brake pad dust that is inside the rotor after the track day, but want to make sure. Has anyone seen a lot of rust from their CC brakes after a track day wash? The rear brakes are perfectly fine no rust on the rims. The rotors don't have any rust on them just in the drill holes. The attached pictures show it all.